"Tapped" and "split" are used interchangeably and should not be.
Some pickups have a "tap" in the coil that allows a portion of the coil to be grounded, resulting in a thinner, brighter sound than the full-power pickup. Both humbuckers and single-coils can have a "tap".
A humbucker can be split, where one entire coil is shut off. Similar in concept to a "tap" but not the same, because technically you can "tap" both coils of a humbucker and still have a humbucking pickup.
Incidentally, transformers also have "taps" on their coils to provide different output levels.
Incidentally,